With the help of innovative technology such as the AXIS, Edge Underground has installed hundreds of thousands of meters of sewer and water pipelines under various ground conditions – from easy to challenging. However, despite these successes, Edge Underground is always looking for ways to increase capabilities and reduce risks to project delivery.  

Maribyrnong development sewer 

When the builders of a new 20-storey development, located beside a busy tram stop in Maribyrnong, needed to install a sewer for the building, they found it difficult to find contractors who would take the job. The development was in the middle of a roadway, featuring tram lines with two lanes either side, and virtually no nature strip. 

The tight space, combined with the close proximity to high voltage power due to the trams, meant excavation equipment was out of the question. To make the job even trickier, the ground consisted of a mixture of hard rock and clay – creating different pressures to drill through whilst maintaining the correct line and grade. 

Unlike most contractors, Edge Underground was up to the task. After a few meetings and an assessment of the conditions, Edge’s team concluded that the job was very achievable with the help of AXIS’ retractable drill rods. 

Unique capabilities of AXIS 

Stuart Harrison, Managing Director at Edge Underground, said, “The AXIS is a versatile, pit-launched, laser-guided machine that can install pipelines on-grade and with pinpoint accuracy to within +/-5mm. I designed it so that the head and cutter style or configuration can be swapped out to deal with changing ground conditions, making it the most versatile machine on the market.

“The rock [at the Maribyrnong project] was probably less than 120 MPA mixed with clay, so it was a real mix. That’s always difficult.

“Whenever you’re in a combination of hard and soft [surfaces], and you combine something trying to pass through with a lot of force to break through the rock, there’ll always be naturally a shift of the drill heads towards the softer condition. 

“The ability of the drill to be able to counteract the different pressures in the ground, and obviously manage that, being able to drill through rock and clay, and still maintain line and grade, it’s something that we pride ourselves on.” 

Now a leading machine on the market, the AXIS has been designed with a host of unique features, such as being able to perform pilot lines and retract to reduce problems occurring from unexpected ground conditions, and safety elements including pressure gages and a Falling Object Protective System (FOPS) safety enclosure.

It facilitated the highly successful sewerage installation in Maribyrnong, with all works being completed in typical business hours, and no additional noise aspects for neighbours in the area. Installation was also completed during low traffic times. 

“I think during that job we had one cutter change. We went from a solid rock to a mixed cutter face, part way through one of the drives. We were able to manage the conditions well,” Mr Harrison said. 

“It was two different drives, installing a 300 PVC, and each of those drives were in that 60 to 70 metre bracket.

“I think it was about seven days of work, and we had the project done.”

Mr Harrison said the project was a strong endorsement of the new innovations Edge Underground had delivered to the microtunnelling industry, but the company still recognised that trenchless technology would need to continue to evolve and improve. 

“We are very much shaping the future of the industry, finding ways to improve equipment so that it is more capable to not only handle the various ground conditions that are out there, but to do it more reliably, more consistently,” Mr Harrison said.

“When we think we’re doing something well, it doesn’t mean we stop looking at it. Even if something is not a problem, we ask if we can do it better.

“As a team we’re all very much passionate about taking everything to a new level. We have guys who wake up in the middle of the night with an idea, and that’s how much they’re into what they do.

“When it comes to designing new equipment or modifying current equipment, the team has a deep breadth of knowledge and expertise to draw on, and they’re diligent in testing and trialling off site. This means that when it is finally used on site, it has been proven and there is no risk to the project.”

The air hammer

This culture of innovation has led to the development of the air hammer, a drilling tool that addresses the challenges of drilling in very hard rock, providing microtunnelling contractors a solution that increases rates of successful pipeline installation, while still maintaining accuracy, productivity and efficiency.

The technology uses air-driven hammers (similar to vertical DTH heads) on Edge Underground’s AXIS laser-guided system. This system is a new technology to the microtunnelling market, enabling drilling in very high strength rock, and has been proven on Yarra Valley Water’s Donnybrook Link Sewer Stage 2 project. 

“It can be operated via the next generation AXIS drill rods with a power enhancing driver, and has been tested and proven with the extra heavy rods of the AdaptX – a new machine on the market with unparalleled capabilities, manufactured by Bournedrill. The system uses high pressure air hammers in sequence – exhausting cuttings through a custom removal system – and is ideal for very high strength rock,” Mr Harrison said. 

“The new system also has environmental and workplace health and safety benefits, enabling small to medium-size pipe diameters to be installed in hard rock faster, with a significant reduction in spoil removal and truck movements compared to open cut methods.” 

With more projects requiring drilling rock on fine grades and the lack of options available that have high rates of success and/or are time and cost efficient, the air hammer is sure to open up many new possibilities for microtunneling contractors.